The Institute of High Energy Physics (IHEP) is China’s largest research institute for high energy physics. At IHEP, more than 1400 full-time employees are enthusiastically trying to unravel the mysteries of the universe at the most fundamental level – from the smallest subatomic particles to the large-scale structures of the cosmos. In addition to fundamental research in particle physics, including astroparticles, IHEP conducts a broad range of interdisciplinary frontier research, e.g., in material science, chemical engineering, and environmental science. Also, IHEP researchers explore modern accelerator technologies, such as electron-positron colliders for the production of Higgs and Z particles, as well as innovative possibilities for high-tech industrialization.
The history of IHEP goes back to the establishment of the Institute for Modern Physics in 1950, a year after the founding of the People’s Republic of China. IHEP itself began as Department No. 1 of this institute, and became an independent research institute in 1973. Today, it is a key player in the international particle physics community. IHEP maintains close ties with other research teams around the world, including official cooperative agreements with about 20 research institutions from 13 countries in Asia, Europe and North America. One example is the US-PRC Joint Committee on High Energy Physics, a collaboration between American and Chinese researchers that has existed for over 30 years and has produced numerous scientific breakthroughs. One big moment was in March 2012, when IHEP researchers discovered a new type of neutrino oscillation during their Daya Bay Reactor Neutrino Experiment – one of the ten biggest scientific breakthroughs of 2012 according to the renowned scientific journal Science.
The Laboratory of Particle Astrophysics, founded in 1951 and later incorporated into IHEP, has also established itself as one of the world’s leading research centers for cosmic background radiation. Other IHEP projects such as the Beijing Electron-Positron Collider (in the tau-charm energy range), the China Spallation Neutron Source Project for the production of spallation neutrons with energies up to 500 kW, and the Jiangmen Underground Neutrino Observatory for the precise determination of the neutrino mass hierarchy are among China’s most important science facilities. Not surprisingly, IHEP also plays a leading role in the Yangbajing Cosmic Ray Observatory, a research facility based in the Tibetan highlands that continuously records ultrahigh-energy cosmic γ-rays with an air shower array exceeding 60,000 m2. Here, too, IHEP's long-standing and reliable relationships within the international high-energy physics community are bearing fruit, including the Sino-Italian research collaboration ARGO-YBJ (Astroparticle Physics Research at Ground-based Observatory Yangbajing), and a Sino-Japanese joint project to study the nature of solar and interplanetary magnetic fields under the influence of solar activity.
One of IHEP’s key projects is the High Energy Photon Source, known as HEPS. It is an extremely powerful synchrotron light source with energies of 6 GeV, and an emittance of less than 60 pm·rad. With a brilliance of more than 1·1022 Sch, HEPS will be one of the world’s brightest synchrotron X-ray sources. In other words, it produces 1022 photons per second, square millimeter, and mrad spatial angle, within a wavelength bandwidth of 1‰. Basically, the HEPS facility consists of an accelerator, beamlines, end stations, and support equipment. There are three accelerators connected in series:
- The Electron Storage Ring has a circumference of 1360 m, a beam energy of 6 GeV, and a maximum current of 200 mA. The electron storage ring consists of 48 modified hybrid 7BA-units to achieve a horizontal natural emittance of less than 60 pm·rad. This structure requires ultrastrong quadrupole and sextupole magnets, thus making the dynamic aperture small and extremely prone to error. Accordingly, the magnets and their supply systems must be manufactured with enormous precision. Also, a special process has to be developed for the construction of the accelerator tunnel to minimize the harmful effects of microvibrations on the beam.
- The Booster is an electron synchrotron accelerator with a circumference of about 454 m. It can be used for accelerating the electron beam from 500 MeV to 6 GeV, before the high-energy beam is injected into the electron storage ring.
- The Linear Accelerator, or Linac, serves as an injector for the booster. It is about 49 m long, has an output energy of 500 MeV and a macro-pulse repetition frequency of 50 Hz. Linac comprises a thermionic-cathode electron gun, a beam bunching system, and a series of S-band constant gradient traveling-wave accelerating structures.
HEPS will be China’s first dedicated high-energy synchrotron radiation source. Planning and licensing procedures for HEPS began in 2016, and completion is scheduled for 2025. The developers of HEPS hope it will greatly boost development in a wide range of science and technology fields. As a multidisciplinary experimental platform, HEPS will support fundamental research that deepens the understanding of matter and its complex interactions at the atomic level. Its extremely high resolution will enable detailed investigations at ultra-minute dimensions. For example, a spatial resolution of up to 10 nm will allow observation of individual nanoparticles, and an energy resolution of 1 meV will allow for deep insights into the most subtle quantum physical processes. In addition, HEPS’s temporal resolution can achieve picosecond level, with a high repetition rate.
The enormously high beam energies and extremely low emittances place the highest demands on the design and operation of the accelerator, beamlines, and end stations. In order to ensure the success of this extremely challenging project, HEPS planners decided to develop the HEPS Test Facility (HEPS-TF) before building the main ring and beamlines. This test facility, which was built from scratch in two and half years, from 2016 to 2018, has proved to be a complete success. Thanks to an innovative MBA-storage ring design, it can reliably deliver the required horizontal emittance of less than 60 pm·rad at a beam energy of 6 GeV. HEPS-TF has also provided the developers with other valuable insights about technology needed for HEPS, e.g., high-gradient quadrupoles, NEG coatings for the vacuum chamber, reliable power supplies for magnets, and Kirkpatrick-Baez optics for fine measurement of the beam profile. In addition, the researchers have used HEPS-TF to test and validate beamlines, a high-energy X-ray monochromator, a nanofocusing probe, a pixel array detector, and other high-precision optical measurement devices for use in HEPS.
With these successful test results, HEPS received the official go-ahead in 2017 for construction of the full-scale facility. HEPS developers had initially proposed 14 beamlines, including a multimodal beamline for hard X-ray nanoprobes, a beamline for structural dynamics, a beamline for microfocusing X-ray protein crystallography, and a high-pressure beamline. After completing the first phase of construction, however, the developers decided to add 70 more beamlines and end stations around the storage ring. Since then, construction has progressed on schedule. The procurement and fabrication of necessary technical equipment, such as accelerator hardware systems, magnets, RF resonators, and a power source for the linear accelerator, are well underway. As a valve supplier, VAT has been closely involved in this exciting, multifaceted project since the early HEPS-TF stage. For example, VAT’s research department developed a special RF valve for one of the beamlines, which performed outstandingly in practical tests. VAT vacuum valves are also used at other central positions in the HEPS or HEPS-TF, primarily from the all-metal 47, 48 and 54 series. "The cooperation with IHEP has been very constructive and trusting, so I am confident that we can continue to contribute our valve know-how to this prestigious research project," says Jerry Zhang, VAT Sales Manager, looking optimistically to the future.